Adapt sources to configurable config.h name
diff --git a/include/polarssl/pk_wrap.h b/include/polarssl/pk_wrap.h
index 91a671e..7baafb9 100644
--- a/include/polarssl/pk_wrap.h
+++ b/include/polarssl/pk_wrap.h
@@ -28,7 +28,11 @@
 #ifndef POLARSSL_PK_WRAP_H
 #define POLARSSL_PK_WRAP_H
 
+#if !defined(POLARSSL_CONFIG_FILE)
 #include "config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 #include "pk.h"